The present invention relates to a system for injecting or dispensing controlled volumes of fluid, particularly for automated injections of very small amounts of fluid into a chamber for sterilizing items such as medical instruments. The present invention particularly relates to a system for removing particulates from the injected fluid and preventing the particulates from depositing on surfaces of the items to be sterilized.
Various sterilants or sterilizing fluids have been used to sterilize medical instruments. One effective way of sterilization is to sterilize the item with a sterilant vapor. In this sterilization process, the item to sterilized is placed in a vacuum chamber. A liquid sterilant is introduced into the vacuum chamber and vaporized therein, so that the item is sterilized by the sterilant vapor.
U.S. Pat. No. 4,643,876 discloses a sterilization method and apparatus. In this method, a sterilizing agent such as hydrogen peroxide is introduced into an evacuated sterilizing chamber where it is vaporized and allowed to disperse onto the items to be sterilized. After a desired period of time, electrical energy is then applied in the chamber to ionize the gas to form a plasma at a power level sufficient to achieve sterilization.
U.S. Pat. No. 4,938,262 and U.S. Pat. No. 4,913,196 issued to the same inventors disclose a pumping apparatus for the fluid injection in a sterilization system, and a method of pumping a sterilizing liquid into an evacuated sterilizing chamber containing an article to be sterilized.
The pumping apparatus for the fluid injection system disclosed in U.S. Pat. No. 4,938,262 provides a fluid supply in the form of a prepackaged closed cell containing a known volume of fluid. The apparatus further includes a mechanism for receiving and positioning the cell, and a cell opener assembly cooperating with the mechanism for penetrating the cell to form an outlet from the cell. A device cooperating with the cell and the receiving mechanism forces the entire volume of fluid out of the cell, thus providing a convenient pumping apparatus for providing a known quantity of fluid.
The systems provided in the above U.S. patents are effective, and have number of advantages over other known systems. Consequently, those sterilization systems disclosed in the above mentioned U.S. patents have been commercialized.
However, further improvements are needed to overcome the disadvantages of the existing vapor sterilization systems. One common problem of existing vapor sterilization system is the deposition of particulates on the surface of the item to be sterilized because stabilizers present in the liquid sterilant, which gives the sterilized item unpleasant and unclean appearance.
Thus, there is a need for a method and apparatus, which eliminates the deposited particulates on the surface, and meanwhile maintains sterilization efficiency.